The present invention relates to a fuel injector and to an internal combustion engine having a fuel injector. More particularly, the invention relates to a fuel injector capable of producing a fuel spray having a superior ignitability and a superior combustibility for use in an internal combustion engine having a fuel injector.
The present invention relates to a fuel injector for forming a complex fuel spray having a superior ignitability and a superior combustibility for use in an internal combustion engine.
An inlet pipe fuel injection device is a device which causes fuel to be injected into an inlet pipe of an internal combustion engine. In addition to an inlet pipe fuel injection device, there is also a direct fuel injection device, which operates to inject fuel directly into a combustion chamber (a cylinder) of the internal combustion engine. Such a direct fuel injection device is disclosed in, for example, Japanese patent laid-open publication No. Hei 5-33,739.
As disclosed in the above stated Japanese patent laid-open publication No. Hei-5 33,739, it is difficult to homogeneously mix fuel which has been injected directly into the combustion chamber with the air being drawn in the combustion chamber. Therefore, it is important to promote the atomizing of the fuel which has been injected directly into the combustion chamber.
To atomize the fuel, up to now, a swirling force has been imparted to the fuel which is injected from a fuel injector. As shown in the above stated Japanese patent laid-open publication No. Hei-5 33,739, a direct fuel injection device having a means for imparting a swirling force to the fuel is disclosed.
Herein, the direct fuel injection device disclosed in the above stated Japanese patent laid-open publication No. Hei-5 33,739, comprises an injection nozzle for injecting fuel from an injection hole, a cylindrical cover having a bottom portion constituting an air chamber at an outer side of the injection nozzle, a swirl chamber which is formed at a side of the bottom portion of the cover so as to communicate with the injection hole of the injection nozzle, and a check valve body which opens and closes the injection hole.
With the above stated conventional direct fuel injection device structure, the swirl chamber has an injection hole and this injection hole introduces air from a tangential direction along an inner peripheral face of the swirl chamber from the air chamber which is constituted in the cylindrical-shaped cover having the bottom portion. In accordance with the above stated air which is injected from the injection hole of the swirl chamber, the fuel injected through the injection hole of the injection nozzle will have a swirl force imparted thereto.
Further, the injection hole and a passage for introducing air from the air chamber into the swirl chamber are provided with a two-stage structure, namely the injection hole and the passage of the swirl chamber are provided at an upper direction and a lower direction (an axial direction of the check valve body) or an upstream side and at a downstream side of the check valve body. Each of the injection hole and the passage of the swirl chamber at the upper direction and the lower direction have the same structure.
However, in the above stated direct fuel injection device, the check valve is arranged at a discharge side. Further, the elements which produce the swirl force are provided at a downstream side of a metering portion of the fuel passage, rather than at an upstream side of the metering portion of the fuel passage.
As a result, after the fuel passes through the metering portion of the fuel passage without having a swirl force imparted thereto, the fuel is subjected to a swirl force for the first time at the downstream side of the metering portion of the fuel passage, namely the swirl force is imparted first in the swirl chamber in response to the applied air.
Accordingly, in the direct fuel injection device structure disclosed in the above stated Japanese patent laid-open publication No. Hei-5 33,739, there is no suggestion to impart the swirl force to the fuel using a portion of the fuel passage upstream of the metering portion of the valve body.
In the conventional technique employed in the above stated direct fuel injection device, the atomization of the fuel is promoted and the spray direction of the fuel and the spreading of the fuel spray have been controlled. However, as stated hereinafter, full consideration has not been given to the shape of the fuel spray, the diameter of the fuel spray and the structure of the fuel spray in which both the ignitability (a spark-in property) and the combustibility (a propagation of fire) are improved in a compatible way.
To attain the optimum property for the spray of fuel which is injected from the fuel injector, it is necessary to consider at least the following three characteristics.
First of all, the first characteristic is the fuel spray shape, and the factors for this fuel spray shape are the spreading angle and the distance or extent of travel of the fuel spray. The second characteristic is the size of a spray fuel particle, in this regard, and it is necessary to lessen the number of spray fuel particles of large size as much as possible and to improve the uniformity of the spray fuel particle size distribution. The third characteristic is the structure of the fuel spray, and, for this purpose, it is necessary to provide a suitable spatial distribution of the fuel particles to be sprayed.
The inventors of the present invention have studied by experimentation various analyses as to how these fuel spray characteristics relate to the combustion properties in the internal combustion engine. As a result of these studies, they have found that, in a case where the spreading angle of the spray of the fuel is large, the inertia force of the fuel spray is weak, with a result that the distance or extent of travel of the fuel spray is short, whereby it is possible to obtain stability in the combustion. Further, on the other hand, by making the spreading angle of the spray of the fuel small, the inertia force of the fuel spray is made strong, with a result that a mixture of air and fuel having a superior ignitability is produced, but it was ascertained clearly that there is a tendency for unburned gas components (HC, CO) in the fuel to increase.